Technical Field
The technique disclosed in this specification relates to methods for measuring the depth of partial penetration of a weld (i.e., methods for measuring the height of lack of penetration), and ultrasonic flaw detectors used in this method.
Description of Related Art
Steel bridges include a steel plate floor for directly supporting a live load. The steel plate floor includes a deck plate, a longitudinal rib, and a cross rib. The longitudinal rib and the cross rib are welded to a back surface of the deck plate. Fatigue cracks might be formed from a weld of such a welded structure due to a long term use. Thus, to secure an adequate fatigue resistance, the specifications for highway bridges provide that the depth of partial penetration of a weld between a deck plate and a U-shaped rib that is widely used as a longitudinal rib and has a U-shaped cross section is 75% or more of the thickness of the rib.
Ultrasonic testing, one of methods of nondestructive testing, is often conducted to test a welding quality on a steel plate floor etc. However, the technique for directly measuring the depth of partial penetration of the weld has not been fully developed.
Conventionally, a welding test has been conducted in advance to determine welding conditions that can ensure the depth of partial penetration satisfying the criterion. Then, the criterion of the depth of partial penetration has been assured by reproducing the welding conditions.